The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Virtually every motor vehicle having a conventional powertrain includes a at least one differential which both directs drive torque to left and right front or rear wheels and allows the wheels to rotate at different speeds without scrubbing or winding up the rear axles as the vehicle turns and negotiates corners. The differential includes a cage or housing which is driven through a hypoid and ring gear assembly and contains two bevel idler gears in constant mesh with two gears connected to the left and right axles which drive the associated wheels. The cage or housing is typically cast iron and includes journal bearings which support a stub shaft upon which the idler gears are disposed. Because of the power applied to the differential and the forces experienced by the gears, shafts and bearings associated with them, the choice of cast iron for the housing is generally accepted as good engineering.
Unfortunately, because of its size, the weight of a cast iron differential housing can be significant. As is well known, automobile manufacturers are under constant and increasing pressure to improve the fuel economy of their vehicles and one of the most direct paths to improved fuel economy is to reduce the weight of the vehicle. Such weight reduction, however, cannot be done at the expense of the ruggedness and service life of the vehicle and its components. Thus, one true challenge of improved fuel economy is the reduction of vehicle weight without any impact on the quality of the vehicle, its ruggedness and service life.
The present invention is directed to both weight reduction of the differential cage or housing and maintenance of its quality and ruggedness.